Consolidation of oil bearing formations



United States Patent 3,333,636 CONSOLIDATION OF OIL BEARING FORMATIONS William L. Groves, Jr., and Henry T. Watanabe, Ponca City, Okla, assignors to Continental Oil Company, Ponca City, Okla., a corporation of Delaware No Drawing. Filed Jan. 27, 1965, Ser. No. 428,558 5 Claims. (Cl. 166-25) ABSTRACT OF THE DISCLOSURE Unconsolidated oil-containing formations are consolidated by introducing a sulfonation agent into the formation in an area surrounding a borehole. In one embodiment, supplemental sulfonatable stock is first introduced.

This invention relates to a method of consolidating an oil bearing subterranean formation. In one aspect, the invention relates to a method for bonding particles of an unconsolidated formation into a permeable unitary mass to prevent movement of particles into the borehole of a well penetrating the formation, the method comprising effecting a sulfonation reaction within the formation.

Many subsurface formations from which oil or gas is produced are unconsolidated formations in which the individual sand particles of the formation are Weakly bonded to one another. When formation fluids are produced from such formations, said particles are carried by the fluids into the borehole of the well where they may plug the well or production tubing and prevent production of oil from the Well. If the oil-bearing formation is under a high pressure, the sand carried into the well frequently flows at a high velocity through borehole equipment and causes serious erosion of the equipment. Both plugging and erosion of the Well equipment make expensive shutdown and workover of the well necessary to allow further production from the well.

Several methods have been used to combat the flow of sands into the well from unconsolidated formations. One of the techniques is to install a slotted liner in the borehole of the well through the pay zone. The slots of the liner are narrow enough to prevent flow of sand through them. Slotted liners frequently fail to accomplish the desired purpose because the movement of the sand around the liner may block the passages in the liner and prevent flow into the well.

Another technique that is employed is to pack fine gravel around a liner to produce a filter bed with small openings through which the sand particles cannot move. The gravel packing technique has the advantage of providing some support to the unconsolidated formation, but sufiers the same disadvantage as the unconsolidated formation that the sand particles are not bonded together and may move to plug passages through which oil flows into the well.

It has been suggested also that the particles in the gravel pack be treated by displacing a resin-forming liquid into the gravel pack to coat the particles and thereafter setting the resin-forming liquid -by condensation or polymerization to bond the particles into a unitary mass. Care must be taken to insure preservation of the permeability of the formation after the resin treatment. One of the difliculties with such a method is finding a suitable resin which can be made to set at condition existing in the pay zone to form a resin of adequate strength and insolubility in formation fluids to produce a bond which will hold the particles together for long periods. One problem encountered in forming a mass of adequate strength is in obtaining satisfactory adhesion of the resin to the particles which are ordinarily covered with oil and water, or both, when the resin-formice ing liquid is displaced through the gravel pack. Because of these difficulties, and the relatively high cost of the large amount of resin required, the use of resin to consolidate formations has not been widely adopted.

It is also proposed, for example in U.S. Patent 3,147,805 to Goodwin et al., issued Sept. 8, 1964, to effect consolidation by oxidative coking of the formation surrounding the borehole, the coking being accomplished by introduction of an oxygen containing gas such as air, at gradually increasing temperatures, into the borehole. This method necessarily requires relatively expensive equipment, such as air compressors and heaters, and also requires a relatively long period of time in which to raise the formation temperature properly.

An object of this invention is to consolidate a formation in a manner requiring very little equipment beyond that normally found on an oil lease to be produced. Another object of the invention is to consolidate a formation in a relatively short period of time and at little expense. Other aspects, objects and the several advantages of this invention will become apparent upon study of this disclosure, including the appended claims.

Briefiy stated, the present invention comprises effecting consolidation of the formation by introducing into the formation surrounding a borehole liquid sulfonating agent. The resulting sulfonation reaction on the oil surrounding the borehole quickly raises the formation temperature and effects coking and consequent consolidation of the formation. In one aspect of the invention, a supplemental sulfontatable stock is first introduced into the formation surrounding the borehole prior to introduction of the liquid sulfonating agent.

The invention will be further illustrated by the following specific example: 600 g. of 20-30 mesh Ottawa sand was saturated with g. of light cycle gas oil. The oilsaturated sand was placed in a Dewar flask with a glass tube placed to reach almost to the bottom. A thermocouple was inserted into the sand beside the glass tube. Sulfur trioxide was introduced in 5 and 10 ml. increments through the glass tube until a total of 65 ml. (approx. g.) had been introduced. The temperature rose to a maximum of 414 F. in less than one hour. There was some reduction in permeability, as shown by the fact that the air flow rate (at 5 p.s.i.g.) dropped from about 10,950 ml./minute before the acid addition to about 8000 ml. minute after the acid addition had been completed. Examination of the sand showed that with the exception of the sand farthest from the end of the glass tube, coking and consequent consolidation had occurred.

The preceding example illustrates use of liquid sulfur trioxide as the liquid sulfonating agent. It is desirable for the sulfonating agent to be liquid in order to obviate the need of expensive or unavailable equipment for the method, such as gas compressors. Other suitable liquid sulfonating agents include oleum.

In certain instances, it is found desirable to increase the reaction effect beyond that possible from the oil present in the formation surrounding the borehole. In these instances, a supplemental material is put into the formation by way of the borehole prior to introducing the liquid sulfonating agent. This supplemental material should be one which is sulfonated readily, for instance an aromatic oil. Other suitable supplemental materials include crude oil residues,

olefins, alcohols and other organic compounds having acably at least about 1 lb. agent per 2 lbs. aromatics. These values apply both to the instance where supplemental sulfonatable material is added to the formation by way of the borehole and to the instance where only material initially present in the formation, i.e. absent supplemental material, is treated. It is noted that these figures are based on aromatic content rather than total hydrocarbon, because of the relative ease of sulfonating aromatics. When no supplemental sulfonatable material is used, the desirable amount of sulfonating agent to be added can be readily determined as by formation analysis, e.g. by core sample analysis.

The sulfonating agent, and also the supplemental sulfonatable material when desired, can be easily introduced into the formation around the borehole by virtue of the fact that they are liquid, and no special equipment is needed either above ground or downhole to effect the consolidation by the present method. The sulfonation reaction is exothermic to the extent of about 40.2 Kcal. per gram mole of, e.-g., S consumed, and this reaction heat effects a coking which in turn binds the unconsolidated particles around the borehole into a competent mass.

Having thus described the invention by providing specific examples thereof, it is to be understood that no undue limitations or restrictions are to be drawn by reason thereof and that many variations and modifications are within the scope of the invention.

We claim:

1. The method of consolidating an unconsolidated formation penetrated by a well bore and containing a hydrocarbon oil which comprises introducing into said formation by way of said wellbore liquid sulfonating agent in amount sufficient to form coke and thus effect consolidation in said formation.

2. The method of claim 1 wherein said liquid sulfonating agent comprises liquid sulfur trioxide.

3. The method of claim 2 wherein said agent is introduced in amount suflicient to eflfect a maximum temperature rise in said formation.

4. The method of claim 1 wherein there is introduced into said formation surrounding said wellbore prior to the introduction of said liquid sulfonating agent a supplemental sulfonatable material.

5. The method of claim 4 wherein said supplemental material comprises an aromatic oil.

References Cited UNITED STATES PATENTS 1/1965 Meadors 1669 7/1966 Prats et al 166-38 

1. THE METHOD OF CONSOLIDATING AN UNCONSOLIDATED FORMATION PENETRATED BY A WELL BORE AND CONTAINING A HYDROCARBON OIL WHICH COMPRISES INTRODUCING INTO SAID FORMATION BY WAY OF SAID WELLBORE LIQUID SULFONATING AGENT IN AMOUNT SUFFICIENT TO FORM COKE AND THUS EFFECTCONSOLIDATION IN SAID FORMATION. 